The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
For advanced neural recordings, there is a growing need for neural interfaces with a large number of independent channels to be able to record complex neural signals. State-of-art approaches utilize neural interfaces with typically 1-128 channels, and each channel is connected to an external electronics system using a single wire (or trace, or electrical conduit). As the number of channels increase, the space necessary for individual wires can become unmanageable and/or impractical for in vivo use.
In order to make high-channel count neural recordings less cumbersome, recent efforts have been devoted to using multiplexing electronics that can combine the signals from multiple channels into a single shared stream. Additionally, multiplexing can be combined with signal amplification, filtering, and signal conditioning strategies to help further reduce the physical size of an electronic module being used to receive the signals from multiple channels.
One specific approach to solving the issue of receiving a large number of independent signal streams being with one electronic module or subsystem is channels using a combined neural interface with active circuitry. In this approach, the neural interface is combined with the active circuitry. This is achieved by fabricating the entire probe and electronics simultaneously. Though the electrical performance of such devices is high, the cost of fabrication increases significantly as wafer real-estate is used for the large footprint of the neural interface. Additionally, if surgical error damages the probe, the entire system needs to be disposed, which adds to cost of this approach. Finally, the yield of such devices is often low, since the performance of the neural interface and electronics are linked. In effect, if either component malfunctions, the entire system needs to be disposed. Bench-top testing of such systems is also difficult since there is no way to interface with individual channels of the neural interface.
Another approach is using active circuitry which is assembled onto a neural interface. With this approach, electronics are permanently assembled onto the neural interface using semiconductor assembly techniques. Though the cost of electronics can be reduced by de-coupling it from device fabrication, the overall cost of assembly is still high. Once assembled, the entire system needs to be disposed of in the event of surgical error. Additionally, it is difficult to independently verify the functionality of the neural interface prior to permanent bonding to the electronics. Upon assembly, if the device is found to be non-functional, the entire system must be disposed of.
Still another approach is using an active electronics headstage. With this approach, the active electronics are kept separate from the neural interface. The active electronics are assembled onto a printed circuit board with a connector leading to the device and another connector leading to the acquisition electronics. A mating standard connector is attached to the neural interface. This allows for the researcher to use multiple designs or iterations of devices with the same active electronics headstage. The disadvantage of this approach is that standard connectors are extremely low density and hence the total number of channels that are practical for most studies is limited to about 32.